The violent resolution of intergroup conflict has plagued the world for all of known history. The major a focus of the proposed research is identifying ways to increase cooperativeness in intergroup interactions. By contrasting the consequences that occur when someone is behaving as part of a group, compared to behaving as an individual, previous research established a clear discontinuity. That is, using a mixed-motive paradigm and face-to-face interaction, repeated group on group interactions typically produce high rates of competition, whereas interactions of two people from those groups are typically characterized by high rates of cooperation. Such discontinuity occurs even though competition yields worse results than mutual cooperation. Existing evidence indicates that such discontinuity is a very robust phenomenon. It is explained partially by the greater tendency of groups than individuals to distrust, or fear, each other and partially by the fact that group members can provide each other with social support for acting in a self-interested, or greedy, manner, whereas individuals have no way of obtaining such social support. The proposed research will attempt to identify ways of reducing discontinuity. Although a research tradition exists for reducing the consequences of conflict by "decategorizing" the participants' cognitions, it is often not feasible or even desirable to do this. Instead, cooperation between intact groups will be induced by interventions that increase trust without increasing vulnerability and that make group's more aware of the long-term consequences of their actions. In order to understand the conditions of applicability, the proposed research will also attempt to identify the individual cognitive processes that support discontinuity and the situational characteristics relating to the outcome domain that. is a necessary condition for the occurrence of discontinuity. If the research is successful it will be possible to specify the conditions under which discontinuity will occur and the methods by which it can be reduced.